The present disclosure relates to the subject matter contained in Japanese Patent Application NO. 2001-388372 filed on Dec. 20, 2001, which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine and a printer. More particularly, the invention relates to an image forming apparatus of a type which visualizes a latent image on an image carrying body by using a developer, and a process cartridge and a developing unit, which are both used for the image forming apparatus.
2. Description of the Related Art
In an electrophotographic machine as a typical example of this type of image forming apparatus, a latent image is formed on an image carrying body such as a photosensitive drum, by a scanning light beam emitted from an optical unit, for example. The latent image is visualized (developed) by using the developer, and transferred onto a recording sheet, such as a recording paper.
In this case, if a two-component developing system, for example, is used, as the toner consumption progresses, toner or toner and carrier are periodically replenished (JP-B-6-12475).
In this type of the technique, an image is transferred onto the image carrying body, while transporting the recording sheet in the substantially vertical direction, and scanning light is laterally incident on the image carrying body.
In this case, a toner replenishment box is disposed in downstream (in a lower part in this instance) of a latent image writing position on the image carrying body. Accordingly, the toner replenishment box does not hinder the operation of writing the latent image onto the image carrying body.
However, in this type of technique, the toner replenishment box is disposed in downstream (in a lower part in this instance) of a scanning light incident position. Therefore, for example, when the amount of toner is increased, the toner amount increase more easily affects the positions of a sheet tray and the optical unit, which are disposed in the lower part, since the volume of the toner replenishment box is increased. Changes to the specification of the machine, caused by the toner replenishing amount change, are not uniform. This makes it difficult to use the image forming apparatus in common for different specifications. An additional problem is that with increase of the toner replenishing amount, the machine size tends to increase.
Further, in a case where the machine is designed so as to allow the toner replenishment box to be pulled out from an upper part of the machine body, it entails that it is difficult to install another device in an upper space of the toner replenishment box. An additional technical problem arises that a dead space is easy to be formed in upstream (in an upper part in this instance) of the scanning light incident position.
Particularly in a case where the process cartridge is equipped with the toner replenishment box, such a technical problem is more remarkable by the amount of its occupied space increase.
The present invention has been made to solve the problems described above. An object of the invention is to provide an image forming apparatus, which is capable of efficiently securing a replenishing function of a developer while satisfying requirements of the size reduction and common usability of the image forming apparatus, and with a minimum chance of forming dead space within the apparatus.
According to embodiments of the invention, there is provided an image forming apparatus including a latent image forming unit and a developing unit. The latent image forming unit forms a latent image on an image carrying body. The developing unit visualizes the latent image formed on the image carrying body by using a developer. A developing housing containing the developer is communicatively connected to a developer replenishment box. The developer replenishment box is disposed in an upstream of a latent image writing position on the image carrying body.